Flashlights are conveniently-sized battery powered portable light sources, which provide the user with a source of illumination. The illumination could be white light or light of a specific color, or even light outside the visible range of wavelengths, such as ultra violet or infrared radiation. The “color” or wave length of the light will depend on the nature of the light source or light sources used in the flashlight. These would typically be either tungsten lamps, ARC lamps, light emitting diodes (LEDs), lasers, or any other emitter.
Because of the general nature of flashlights and their wide range of applications, it is very desirable for a flashlight to be able to emit, at the user's direction, different levels of light output, different colors or wavelengths of light, and/or other different operating modes beyond “on and “off”. This can be accomplished using multiple light sources or a single light source, which can be adjusted to provide different levels of light output.
The principal light source used in flashlights is the tungsten filament lamp, as alternatives suffer inadequate illumination, or excessive battery consumption. Tungsten filament lamps, however, are limited in their ability to generate extremely high light levels. Arc lamps or HID lamps are capable of higher brightness levels.
However, HID lamps do not start up simply by applying the operating voltage. Such lamps require a start up mode that is very different from the operating mode. If the start up mode were continued indefinitely, energy would be wasted, operation compromised, and damaged risked. Start up mode requires a pulsing of higher than normal voltage to strike an arc. Thus, existing lamps use a limited duration start up mode. However, this may overstress the lamp or be inadequate duration, depending on conditions.
Flashlights having multiple operating modes (more than just on and off) have employed a variety of different switch types, including slider switches. In some existing systems, the switching system consists of a mechanical contact arrangement where the physical axial displacement of a switch system element (either by direct finger or thumb pressure or by rotation of a tail cap or head of the flashlight) causes first one lamp to be connected to the battery, and additional applied pressure or flashlight element rotation causes the second lamp to be connected to the battery. In some cases, the design is such that the first lamp is disconnected when the second lamp is connected to the battery. In other cases, the first lamp remains connected when the second lamp is connected. For some applications, the contacts may be fouled by arcing when the contacts are in close proximity, but not firmly in contact.
It should be noted that the term “lamp” is used in its most general meaning, namely that of any light source (which could be a tungsten filament lamp, an LED, a laser or an ARC Lamp) of any wavelength.